1. Field of the Invention
The invention relates to electromagnetic actuators for a control valve of a fuel injector for internal combustion engines.
2. Background Art
Co-pending U.S. patent application Ser. No. 10/197,317, filed Jul. 16, 2002, entitled xe2x80x9cElectromagnetic Actuator and Stator Design in a Fuel Injector Assemblyxe2x80x9d now U.S. Pat. No. 6,565,020, discloses an injector assembly for an internal combustion engine wherein a plunger body, a valve body and nozzle assembly are arranged in a linear, stacked relationship. The valve body encloses a magnetic core. The magnetic core is surrounded by windings that are energized to create a magnetic circuit, which creates a magnetic force that draws an armature connected to a control valve towards the magnetic core to close the control valve. The magnetic core has a generally E-shaped cross section having a central inner portion and outer portions. The magnetic circuit comprises the central portion of the magnetic core, the armature, and the outer portions of the magnetic core.
The co-pending patent application and U.S. Pat. No. 6,565,020 are owned by the assignee of the present invention.
The separate magnetic core components of the design of the co-pending patent application are assembled with the valve body prior to assembling the control valve and valve actuator. It would simplify manufacture of the fuel injector if the magnetic core could be made integral with the valve body. Such a core design also would be more economical to manufacture than a magnetic core with separate components.
The electromagnetic actuator of the invention is adapted for use with a control valve module described in the co-pending application identified above.
The actuator of the invention comprises a modular valve body having an opening therein and a coaxial bore extending at least partially through the valve body. A control valve, having an armature attached thereto, is inserted into the bore in the valve body. A magnetic core, encircled by windings, is inserted into the opening in the valve body. A valve spring biases the armature away from the magnetic core, and a retainer ring holds the windings and the magnetic core in the opening in the modular valve body. The windings, when energized, produce a magnetic circuit that includes the modular valve body, magnetic core, armature, and retainer ring to attract the armature towards the magnetic core.
The valve body of the actuator of the invention comprises an integral part of the magnetic circuit, unlike the magnetic core of generally E-shaped cross-section in the design disclosed in the co-pending application. The invention simplifies the manufacturing and assembly process and reduces the cost of the fuel injector. If the inner portion of the core is formed by laminated windings, the magnetic performance of the actuator is enhanced.
In accordance with one embodiment of the invention, both the inner and outer magnetic core portions are made as a part of the valve body, which eliminates the need for a separate inner core portion. The core windings are held in place by a retainer ring. In accordance with another embodiment of the invention, the retainer ring can be eliminated if the armature is sized to overlie the core windings. Thus, the windings can serve the secondary function of a retainer. Such a design would be useful if the resulting increased mass of the armature is not detrimental to the effective performance of the injector.